In recent years, grid computing has been extensively researched in both the academic field and the practical application. As a distributed computing model, grid computing represents a new type of system. Such a system can combine heterogeneous computing resources such as computers, storage space, sensors, applications, and experimental results together through Internet connections, thus enabling a wider range of user groups to access the resources conveniently. For example, when a user requests some computing and data resources, the network may provide such resources through the Internet seamlessly, transparently, and dynamically in a way very similar to the mode of supplying electric power to terminal users in an electric power network.
However, grid computing aims to provide secure grid service resources for legal users. Therefore, security is one of the top priorities in grid computing. In order to prevent illegal users from accessing grid resources, mutual authentication needs to be performed between the user and the server.
An effective and practical password-based authentication solution is provided in the prior art to handle authentication. The solution includes the following steps:                U represents a user;        S represents a trusted server;        ID is an opened identity of the user;        pw represents a low-entropy password of the user;        K represents a server key;        p, q are two big prime numbers, where q|p−1;        g: GF(p) is a generator whose mid-order is q;        E(x, y) is a symmetric encryption algorithm, which encrypts y using x as a key; and        H( ) is a secure unidirectional Hash function.        
First, the server stores the (ID, E(K, pw)) in the database through a key (K). For ease of description, mod p is omitted.